The proposed studies attempt to reveal the nature of synaptic regulation of neurotransmitter function in adrenergic secretory cells. The isolated purifed bovine adrenal chromaffin cell in culture--a preparation recently developed in my laboratory--will be utilized to assess the roles that cyclic nucleotides, calcium catecholamines, and protein phosphorylation might play in the regulation of tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of catecholamines. By assessing: 1) precursor pools and dynamics, 2) hydroxylation of tyrosine by the intact cell, 3) kinetic properties of tyrosine hydroxylase isolated from the intact cell, 4) the phosphorylative state of tyrosine hydroxylase and 5) other proteins in the cell, we will be able to describe the cellular processes as they affect 6) the final, common pathway in the regulation of adrenergic function: secretion of catecholamines. By investigating the various processes that can influence catecholamine output from these cells, we hope to be able to determine the principles of regulation of adrenergic function in response to the ongoing, physiological activity in adrenergic systems.